1. Technical Field
The present invention relates to a timepiece with a wireless function that can receive radio waves.
2. Related Art
Timepieces with wireless communication functions are now common. One use for such wireless communication functions is to receive satellite signals and acquire the current time from positioning information satellites such as GPS (Global Positioning System) satellites.
When the timepiece with a wireless communication function is a wristwatch, for example, an antenna that can provide good reception in a confined space is needed.
Wristwatches that can function as a terminal of a satellite communication system, and wristwatches that can send and receive radio broadcast signals, are taught in Japanese Unexamined Patent Appl. Pub. JP-A-2000-59241, JP-A-2001-27680, and JP-A-H10-160872.
The wristwatch described in JP-A-2000-59241 has a C-shaped loop antenna with a dielectric substrate around the display unit, and uses the metal base of the wristwatch as a ground plate.
The wristwatch described in JP-A-2001-27680 has a GPS antenna disposed beside the display unit of the wristwatch. The GPS antenna is affixed with double-sided tape to the metal case of the wristwatch.
The wristwatch described in JP-A-H10-160872 disposes the antenna and communication circuit together in a plastic bezel, and enables easily adding a transmission and reception mechanism to the wristwatch by simply installing the bezel. The antenna is covered by the bezel and hidden from view.
In addition to such practical functions as displaying the time and communication, however, the feel and appearance of high quality is also desirable in a timepiece.
Metals that have been given a precision finish are often used for the case, dial, and other external parts of such timepieces. The communication antenna and other functional parts are, as much as possible, housed inside or covered so that the appearance is not impaired.
The configurations described in JP-A-2000-59241 and JP-A-2001-27680 have the communication antenna located beside the display unit and obviously exposed to the outside, and therefore cannot be used when a high quality appearance is desired.
The configuration described in JP-A-H10-160872 avoids problems with appearance, but cannot assure sufficient antenna performance. More particularly, while the communication antenna is not exposed with JP-A-H10-160872, there is no ground plate.
In addition, while a metal case and dial afford a desirable appearance, their conductivity blocks electromagnetic waves from reaching the inside. Sufficient antenna performance therefore cannot be achieved when the antenna is housed inside the metal case and dial.